As means for appropriately changing the size of loops of courses in the flat knitting operation, there is known an apparatus in which amonng knitting cams of a flat hosiery knitting machine, loop size-changing knitting cams are disposed on both the sides of a raising cam, respectively, each of these, loop size-changing, knitting cams is formed into left and right parts so that the position can be changed, and the loop size-changing knitting cams act on higher and lower butts of latch needles or jacks independently to change the size of loops of the respective latch needles or jacks independently. In this known apparatus, the pattern of the knitted fabric is determined according to arrangement of latch needles or jacks of lower and higher butts in a needle groove, and in order to change this pattern, it is necessary to change vertical arrangement of butts of the latch needles or jacks.